Sunday, March 21, 2010

A Bayesian Brain is a Freudian Brain

Anna O.'s Default Mode. Anna O. is the famous patient whose case was included in Studies on Hysteria by Josef Breuer and Sigmund Freud. Midsagittal brain image (PALS cortical surface atlas, Van Essen 2005) shows resting state functional connectivity in three cortical networks: (i) dorsal attention system (DAS, blue); (ii) the salience system (light green); and (iii) the default mode network (orange). [Taken from Fig. 2 of Carhart-Harris & Friston 2010. Justin Vincent and Randy Buckner are not to blame.]

"Given the nature of this synthesis, different readers will find merit in different aspects of it."

-R. L. Carhart-Harris and K. J. Friston, The default-mode, ego-functions and free-energy: a neurobiological account of Freudian ideas
Our previous post (Friston is Freudian) presented an overview of the new megawork [metawork?] of Carthart-Harris & Friston (2010), an ambitious project to map selected Freudian ideas (id and ego but not super-ego)1 onto the brain's large-scale intrinsic networks as revealed by modern neuroscientific methods (fMRI, resting state functional connectivity, intracranial EEG recordings, and computational models). As mentioned before, they marshalled the neuroscientific concepts of Bayesian Brain, Default Mode Network, Free Energy, Gamma Oscillations, Prediction, Prediction Error, Theta Oscillations, and Top-Down Control in support of their neuropsychoanalytic scheme. After reading the article, I was amazed at the boldness and creativity it took to develop this framework. The 70 pages of Supplementary Data included 493 quotes from Freud.


Freud's Model of the Mind: "The ego is not sharply separated from the id; its lower portion merges into it.... But the repressed merges into the id as well, and is merely a part of it. The repressed is only cut off sharply from the ego by the resistances of repression; it can communicate with the ego through the id." (From Freud's 1923 paper "The Ego and the Id")

However, not all 493 quotes were used in support of selected characteristics of the ego (Secondary Process - ‘normal waking consciousness of adult humans’) and the id (Primary Process - ‘altered’ or ‘non-ordinary’ states of consciousness). For instance, I don't see Q439 (on early childhood sexuality) anywhere in Table 1 or the text:
The sexual life of human beings exhibits an efflorescence which comes to an end at about the fifth year and it followed by what is known as the period of latency (till puberty)… [Q439, Freud, 1939, p. 75]
Likewise, the super-ego is neglected (see also Footnote 1):
If we consider once more the origin of the super-ego as we have described it, we shall recognise that it is the outcome of two highly important factors, once biological and the other of a historical nature: namely, the lengthy duration in man of his childhood helplessness and dependence, and the fact of his Oedipus complex, the repression of which we have shown to be connected with the interruption of libidinal development by the latency period and so with the diphasic onset of man’s sexual life... [Q344, Freud, 1923, p. 35]
But let's return to what they did include in their synthesis. C-H and F want to establish the construct validity of Freudian concepts (id and ego) to operationalize them and subject them to empirical scrutiny. In brief, the ego (normal adult human consciousness) is more or less equated with activity in the brain's "default mode" network (Raichle et al., 2001), measured as spontaneous fluctuations in the BOLD signal during unconstrained cognition. Activity in the default mode network (DMN)2 is anti-correlated with activity in "active task" networks, which are engaged by typical neuroimaging experiments. In contrast to the ego, the limbic id is equated with unusual and altered states of consciousness, as seen in psychosis, the aura of temporal lobe epilepsy, hallucinogenic states, and REM sleep.3

Added to this is a key concept in recent Fristonian thought. The "free-energy principle" is the idea that the brain is an inference engine (Helmhotz, 1860) that makes probabilistic predictions about the world (i.e., its external and internal input) based on past experience, then updates these predictions based on current events (Friston, 2010). The goal is to minimize "free-energy"4 or prediction error.



In The Prophetic Brain, Friston attempts to explain this for a lay audience:5
The emerging picture is that the brain makes its inferences by minimizing the free-energy of messages passing between hierarchical brain regions. ... Information from these exchanges passes on to “higher” levels (those responsible for cognitive functions) through “bottom up” connections. The higher levels respond with “top down” messages to the lower levels. This reciprocal exchange repeats itself hierarchically, back and forth, layer by layer, until the highest level ... becomes engaged. Only then will you consciously register a perception. In this scheme, the free-energy is essentially the collective prediction error over all levels of the hierarchy: Top-down cognitive messages provide predictions based on representations from above, and lower sensory levels reciprocate with bottom-up prediction errors. These “error messages” drive encoded representations (such as neuronal activity) to improve the predictions for lower levels (that is, to reduce free-energy).
This is a variant on the Bayesian Brain view that has been applied to spike coding in computational neuroscience. Friston and colleagues (Friston et al., 2006; Friston, 2009; Friston, 2010) have extended this approach to neuroimaging data.



To learn more, a good place to start is this New Scientist article, with a title that reflects the ambitions of some of the researchers quoted therein:
Is this a unified theory of the brain?

. . .

Friston’s ideas build on an existing theory known as the “Bayesian brain”, which conceptualises the brain as a probability machine that constantly makes predictions about the world and then updates them based on what it senses.

The idea was born in 1983, when Geoffrey Hinton ... and Terry Sejnowski ... suggested that the brain could be seen as a machine that makes decisions based on the uncertainties of the outside world. In the 1990s, other researchers proposed that the brain represents knowledge of the world in terms of probabilities. Instead of estimating the distance to an object as a number, for instance, the brain would treat it as a range of possible values, some more likely than others.

A crucial element of the approach is that the probabilities are based on experience, but they change when relevant new information, such as visual information about the object’s location, becomes available. “The brain is an inferential agent, optimising its models of what’s going on at this moment and in the future,” says Friston. In other words, the brain runs on Bayesian probability. Named after the 18th-century mathematician Thomas Bayes, this is a systematic way of calculating how the likelihood of an event changes as new information comes to light.
How are all of these biological and mathematical observations related to Freudian psychology? The helpful table below gives a summary.

Table 2 (Carthart-Harris & Friston, 2010). Some points of contact between Freud’s account of the mind and empirical findings in neurobiology
  • The overlapping phenomenology of REM sleep, early and acute psychosis, the temporal lobe aura and the hallucinogenic drug state.
  • All these states have been independently compared with each other previously and described independently as conducive to primary process thinking.
  • The neurophysiology of these non-ordinary states is remarkably consistent both empirically and with Freud’s descriptions of the ‘free-flowing’ energy of the primary process.
  • LSD given immediately prior to or during sleep promotes REM sleep.
  • The overlap between Freud’s descriptions of the give-and-take relationship between ego–libido and object–libido and the give-and-take relationship between the DMN and its anti-correlated networks.
  • The concordance between Freud’s descriptions of the secondary process working to minimize free-energy and the free-energy account of the hierarchical organization of intrinsic networks working to minimize prediction errors.
  • The integrated, compound nature of the DMN and Freud’s descriptions of the integrated, compound nature of the ego.
  • The development of functional connectivity between the nodes of the DMN during ontogeny, a process that parallels the emergence of ego-functions.
  • Freud’s account of the ego as a recipient and product of regular endogenous activity concerned with drive, memory and affect and the functional and structural connectivity of the DMN’s cortical nodes with limbic structures concerned with drive, memory and affect.
  • Freud’s description of the ego as a tonic reservoir of activity and the high resting-state metabolism of the DMN.
  • Freud’s account of the ego as the seat of the sense-of-self and studies showing increased activity in the DMN during self-referential processing and a failure to deactivate the DMN in pathology characterized by withdrawal.
After reading the 10 page presentation of this formidable new framework for the mind we come to the Discussion, where Carthart-Harris and Friston make some concessions:
"For those opposed to Freud, who would rather see his constructs dissolved into pure phenomenology and neurobiology, we put up little resistance (e.g. Q176). Phenomenology and neurobiology can stand alone."

-Carthart-Harris & Friston (2010)
In essence what we've seen here is a surprising form of Reverse Reductionism, or Expansionism: a mapping of brain states onto the concepts of id and ego. Am I the only one who is unaware of this new trend in neurosciences/cognitive sciences? Although it is an impressive and scholarly treatment of Freud in light of the latest neurophysiological and computational principles, one can view the entire synthesis as a series of metaphors. The authors concede as much:
"Freud’s writings contain many useful heuristics for exploring global brain function, especially in non-ordinary states of consciousness."
Finally, we have an appeal to the long-lasting influence of Freud:
"If [Freud’s theories] were built on false inference and loose philosophy, it is unlikely they would have endured in the way that they have."
Just because the Freudian view has persisted doesn’t mean it’s correct. What about creationism? Or intelligent design? While we're on the topic of pseudoscience, are some of the less "scientific" interests of Freud (e.g., telepathy) irrelevant here? It seems to me that picking and choosing which Freudian ideas you want to implement in the brain and which you want to discard is akin to picking and choosing which biblical laws in Leviticus you do (or do not) want to follow.

Footnotes

1 They seem to have dispensed with the super-ego. Perhaps because that would entail discussion of the Oedipus complex?
Freud's theory implies that the super-ego is a symbolic internalization of the father figure and cultural regulations. ... The super-ego acts as the conscience, maintaining our sense of morality and proscription from taboos. Its formation takes place during the dissolution of the Oedipus complex and is formed by an identification with and internalization of the father figure after the little boy cannot successfully hold the mother as a love-object out of fear of castration.

...The concept of super-ego and the Oedipus complex is subject to criticism for its sexism. Women, who are considered to be already castrated, do not identify with the father, and therefore form a weak super-ego, leaving them susceptible to immorality and sexual identity complications.
2 For a critique of the DMN (also called the "resting state" network) see Morcom & Fletcher (2007) and RESISTING A RESTing State.

3 These altered states of consciousness were viewed in an interchangeable fashion and related to hippocampal theta activity. Does this mean that spatial navigation, learning, and memory are considered primary process modes of thought?

4 "An information theory measure that bounds or limits (by being greater than) the surprise on sampling some data, given a generative model" (Friston, 2010).

5 Friston's unhelpful onion metaphor was removed.

References

Carhart-Harris, R., & Friston, K. (2010). The default-mode, ego-functions and free-energy: a neurobiological account of Freudian ideas Brain DOI: 10.1093/brain/awq010

Friston K. (2009). The free-energy principle: a rough guide to the brain? Trends Cog Sci. 13:293-301.

Friston K. (2010). The free-energy principle: a unified brain theory? Nat Rev Neurosci. 11:127-38.

Friston K, Kilner J, Harrison L. (2006). A free energy principle for the brain. J Physiol Paris 100:70-87.

Helmholtz H. (1860/1962). Handbuch der Physiologischen Optik. English translation. In: Southall JPC, editor. Dover: New York. Vol. 3.

Morcom AM, Fletcher PC. (2007). Does the brain have a baseline? Why we should be resisting a rest. NeuroImage 37:1073-82.


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6 Comments:

At March 22, 2010 12:06 AM, Anonymous Anonymous said...

Nice work! Thanks for summarizing Helmholtz with such clarity.

 
At March 24, 2010 2:58 PM, Blogger Mike said...

This comment has been removed by the author.

 
At March 29, 2010 8:26 AM, Anonymous Allison said...

This was a great post. I'm still floored by the fact that the Friston/Freud paper was published. For years, researchers in the soft sciences have been struggling to formulate "models" that explain fact. This reminds me of the quote by statistician George EP Box, who said, "All models are false but some models are useful." Sadly, I really can't fathom any way in which the model offered up in that manuscript could possibly be useful.

 
At March 30, 2010 11:18 AM, Blogger Neuroskeptic said...

This seems like one of those ideas that's either really clever, or really stupid, and so opaque that it's hard to tell. I need to read a lot more to work it out.

 
At April 01, 2010 6:59 AM, Blogger The Vlad said...

"This seems like one of those ideas that's either really clever, or really stupid, and so opaque that it's hard to tell."

Quintessential neuroscience then?

 
At April 13, 2010 2:49 PM, Blogger micaela said...

This is the beginning of my wildest career dream coming true, the possibility of methodologically sound work from "hard core" neuroscientists that dare to be more in the Symbol than in the Diabol side... That won't dismiss as "psychoanalytical bla bla" the insights that you necessarily come across when you are both a clinical psychiatrist with psychoanalytical training and a neuroscientist... Am happy! :)

 

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